Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $16.33   7.526%   $17.559   $17.56   $17.55   $17.60  
  Purchase #2 $52.68   11.361%   $58.665   $58.67   $58.65   $58.70  
  Purchase #3 $119.91   9.800%   $131.6612   $131.66   $131.65   $131.70  
  Purchase #4 $214.45   5.645%   $226.5557   $226.56   $226.55   $226.60  
  Purchase #5 $214.86   10.812%   $238.0907   $238.09   $238.10   $238.10  
  Purchase #6 $240.97   13.810%   $274.248   $274.25   $274.25   $274.20  
  Purchase #7 $188.49   13.612%   $214.1473   $214.15   $214.15   $214.10  
  7 purchase totals = $1,047.69       $1,160.9269   $1,160.94   $1,160.90   $1,161.00